The Grass Valley plate. Relief from Copernicus GLO-30; rivers and lakes from USGS NHD; watersheds from the USGS Watershed Boundary Dataset; roads and city limits from Census TIGER 2024.
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1° on Nov. 15, 2014, the coldest reading for this week of the year since 1897. Next is 2° in 1955.
Grass Valley’s center stands about 2,260 ft above sea level. Within three miles the land runs from 1,500 ft to 2,430 ft, a difference of 930 ft: steep hill country.
Under the town center the state geologic map shows Wanapum Basalt, from the Middle Miocene, 12 to 16 million years old.
The section below crosses 2 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 8×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Basalt. Age: Middle Miocene, 12 to 16 million years old. About 19 mi of the line.
Basalt. Age: Early Miocene to Middle Miocene, 12 to 23 million years old. About 5 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale.
Heights from Copernicus GLO-90 (a surface model: it includes buildings and tree canopy); summits from USGS GNIS; rivers from USGS NHDPlus HR; rock from the USGS State Geologic Map Compilation.
A raindrop that lands in Grass Valley reaches the Pacific Ocean by way of the John Day and the Columbia: about 270 river miles.
Lake on the way: Lake Umatilla.
210 miles of the trip are on the Columbia.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Grass Valley; river miles along the main stem, rounded.
Grass Valley has a dry-summer warm-summer continental climate. Summer afternoons average 84° in July; winter nights fall to about 24° in January. A normal year brings about 17 inches of snow; with the rain, that comes to about 11 inches of water.
On November 14 Grass Valley normally reaches 49° and falls to 29°. The record high is 71°, in 1999; the record low 2°, in 1955. The most rain on this date, 0.55 in, fell in 1965.
Normals 1991–2020 and records since 1897 at Moro, 9 miles north-northeast, 390 ft lower. NOAA, through RCC-ACIS.
